The 5th and 6th Centuries AH/11th and 12th Centuries AD contained both positive as well as negative features. The most positive feature of this period was that the sciences that had emerged in the previous period gained expansion and reached their glory in a number of areas. On the other hand, the negative feature of this period was that freedom of thought and intellectual tolerance gradually came to be replaced by narrow-mindedness, bias, and prejudice. This trend was initially marked with disputes and accusations and then bloodshed, finally prompting a move on the part of the Ghaznavid ruler Soltān Mahmud (ruled 389-421 AH/999-1030 AD) to massacre the Shiites and to put their libraries on fire during his attack on the Rey City. The outcome of this attitude was that knowledge and philosophy came to be forced to serve the interests of particular beliefs, as a result of which their natural trends of growth and evolution came to be aborted.